The present invention relates to an optical matrix switch, and in particular to an optical matrix switch with improved coupling efficiency.
Conventional optical matrix switches, such as the ones disclosed in U.S. Pat. No. 4,580,873 issued Apr. 8, 1986 to Frank Levinson, include a linear array of collimating lenses (e.g. graded index lenses) mounted perpendicularly to a linear array of receiving lenses with a two-dimensional array of reflecting elements mounted therebetween. In use, optical fibers are connected to each of the lenses, and the reflecting elements are selectively actuated for directing light signals, exiting from the collimating lenses, to the desired receiving lenses. Accordingly, any light signal entering the switch through the input optical fibers can be directed to any one of the output optical fibers. However, coupling losses varied greatly depending upon which output optical fiber was selected, due to the variances in the signal path lengths from the input optical fibers.
Various devices have been developed in an attempt to improve the efficiency of the signal transfer, such as the switch disclosed in U.S. Pat. No. 5,841,917, issued Nov. 24, 1998 to Roger Jungerman et al. In this switch, the input optical fibers and the output optical fibers are staggered, thereby ensuring that all of the signal path lengths through the switch are equal. This is important because the best coupling efficiency occurs when the system is symmetrical and the Gaussian beam waist is centered between the two lenses. Unfortunately, this switch is quite bulky, relatively difficult to install, and relatively expensive to manufacture.
An object of the present invention is to overcome the shortcomings of the prior art by providing an optical matrix switch with minimal coupling loss variation.
a first substantially linear array of collimating lenses defining input ports for transmitting light beams from input waveguides, each light beam having a waist along its length, at which the beam""s diameter is at a minimum;
a second substantially linear array of focusing lenses defining output ports for receiving the light beams from the first array of lenses and transmitting the light beams to output waveguides; and
a two-dimensional array of Mxc3x97N controllable elements aligned between the two arrays of lenses at respective intersection points of the light beams, whereby in a first state a controllable element will redirect a light beam from an input port to an output port, and whereby in a second state the controllable element allows a light beam to pass unobstructed;
wherein a plurality of the collimating lenses, which transmit light via a Pxc3x97P array of the controllable elements, are adapted to focus the waists of the light beams being transmitted thereby onto respective controllable elements, which are disposed on a diagonal line extending across the Pxc3x97P array of the controllable elements, in which Pxe2x89xa6the lesser of M and N.